1. Technical Field
The present invention relates to a robot arm and a robot.
2. Related Art
A multi-joint robot arm in which a plurality of arm members (elements) are connected one another has been known. JP publication No. 2010-284777 discloses a multi-joint robot arm that has housing (a motor case) in which a motor is mounted. A cable is wound around an outer circumference of the housing. An outer diameter of the housing is substantially the same in a center axis direction.
However, in the multi-joint robot arm disclosed in JP publication No. 2010-284777, because the outer diameter of the housing is substantially the same in the center axis direction, a length of the cable that is wound around the housing is proportionally longer as the outer diameter and the number of wound are larger. Thus, the following problems occur: the costs of a cable may increase and work hours for cabling increase. Thus, one of objects of the present invention is to provide a robot arm and a robot in which a length of a cable is as short as possible.
JP publication No. H09-141593 also discloses a multi-joint robot arm that has housing (a motor case) in which a motor is mounted. Heat that is generated by an operation of the motor is transferred via the housing.
However, in the multi-joint robot arm disclosed in JP publication No. H09-141593, because a thickness of a wall of the housing is substantially the same in a center axis direction, it is hard to intentionally design about a motor heat transfer preferential path, i.e., the heat transfer preferential path is toward an end effector side or a base side. Thus, one of objects of the present invention is to provide a robot arm and a robot in which heat generated by a motor is surely transferred to the base side.
A robot arm configured by coupling a plurality of arm sections and a robot including the robot arm have been known (see, for example, Patent Literature 1). In the robot arm, a coupling portion of the arm sections is a joint. The arm sections can be bent or twisted by the joint. The external shape of each of the arm sections is formed in a pillar shape (e.g., a columnar shape). The outer diameter of the arm section is substantially fixed along the center axis direction thereof.
The related art is described in JP-A-2010-284777.
However, when the arm sections having the substantially fixed outer diameter are bent by the joint between the arm sections, since the outer diameter is fixed, the outer circumferential section of one arm section and the outer circumferential section of the other arm section interfere with each other (collide with each other) relatively early after the start of the bending. Therefore, a movable range (a turning range) of the arms is relatively narrow.